JP6911778B2 - Radar device - Google Patents

Description

The present disclosure relates to a radar device that detects an object by transmitting and receiving radio waves via a plurality of antennas.

Patent Document 1 describes a transmitting antenna unit having a plurality of transmitting antennas arranged in a row along a preset arrangement direction and a receiving antenna unit having a plurality of receiving antennas arranged in a row along the arrangement direction. A radar device with and is described.

In the radar device described in Patent Document 1, the arrangement interval of the two transmitting antennas is 4d, and the arrangement interval of the four receiving antennas is d. Therefore, in the radar device described in Patent Document 1, a virtual array is formed in which eight virtual receiving antennas are arranged in a row along the arrangement direction at an arrangement interval d.

Japanese Patent Application Laid-Open No. 2011-526370

However, in the radar device described in Patent Document 1, the arrangement interval of the receiving antenna coincides with the arrangement interval of the virtual receiving antenna, and the arrangement interval of the receiving antenna is narrow, so that the isolation of the receiving channel is poor and the object In some cases, the accuracy of orientation detection was reduced.

An object of the present disclosure is to improve the detection accuracy of the orientation of an object.

One aspect of the present disclosure is a radar device (1) including a transmitting antenna unit (3), an oscillating unit (21), a modulation unit (22), a receiving antenna unit (4), and a processing unit (6). Is.
The transmitting antenna unit has a plurality of transmitting antennas arranged in a row along a preset arrangement direction at a preset first interval. The oscillator generates a continuous wave common signal. The modulation unit rotates the phase of the branched signal for each preset repetition period with a different phase rotation amount for each of the plurality of branched signals obtained by branching the common signal to the same number as the plurality of transmitting antennas. By performing phase shift modulation, a plurality of transmission signals input to a plurality of transmission antennas are generated. The receiving antenna unit has a plurality of receiving antennas arranged in a row along the arrangement direction at a second interval set differently from the first interval. The processing unit relates to an object that reflects the radiated wave from the transmitting antenna unit based on a plurality of signal components corresponding to the plurality of transmitting signals extracted from each of the plurality of received signals received by the receiving antenna unit. Generate information.

Then, in the radar device of the present disclosure, the plurality of transmitting antennas and the plurality of receiving antennas form a virtual array in which a plurality of virtual receiving antennas are arranged in a row along the arrangement direction. Further, the first interval is equal to the multiplication value of the minimum interval which is the minimum value of the arrangement interval of the plurality of virtual receiving antennas and the first multiple which is an integer of 2 or more, and the second interval is the minimum interval and 2 It is the above integer and is equal to the multiplication value with the second multiple set so as to be different from the first multiple. And the first and second multiples are relatively prime.

In the radar device of the present disclosure configured in this way, the arrangement interval of the plurality of receiving antennas is more than twice the arrangement interval of the virtual receiving antennas, and the physical receiving channel interval can be widened. The isolation between the antennas can be improved, and the detection accuracy of the orientation of the object can be improved.

In addition, the reference numerals in parentheses described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiment described later as one embodiment, and the technical scope of the present disclosure is defined. It is not limited.

It is a block diagram which shows the structure of a radar apparatus. It is a figure which shows the relationship between a transmitting antenna and a receiving antenna, and an object. It is a figure which shows the arrangement of the receiving antenna in a virtual array. It is a figure which shows the arrangement of the transmitting antenna and the receiving antenna, and the arrangement of the receiving antenna of a virtual array. It is a figure which shows the function of an oscillator part. It is a figure which shows the example of the phase rotation amount used for the phase shift keying in a modulation part. It is a flowchart which shows the object detection process. It is a figure which shows the combination pattern of the phase rotation amount which can be selected and cannot be selected. It is a figure which shows the selection example of the phase rotation amount. It is a figure which shows the example of the same object peak group appearing in a velocity spectrum. It is a flowchart which shows the information generation processing. It is a figure which shows the estimated locus of a target. It is a figure which shows the reception spectrum. It is a figure which shows the directional spectrum when the target directional is estimated using the MUSIC method. It is a figure which shows the arrangement of the receiving antenna of the virtual array in the case of d _T = 2d and d _{R = 3d.} It is a figure which shows the arrangement of the receiving antenna of the virtual array in the case of d _T = 3d and d _{R = 4d.} It is a figure which shows the arrangement of the receiving antenna of the virtual array in the case of d _T = 3d and d _{R = 5d.} It is a figure which shows the transmitting antenna and the receiving antenna arranged in a row along the height direction of a vehicle. It is a figure which shows the transmitting antenna and the receiving antenna arranged along the arrangement direction and the vertical arrangement direction.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
The radar device 1 of the present embodiment is mounted on a vehicle and detects various objects existing around the vehicle. The radar device 1 is a MIMO radar that transmits and receives radio waves simultaneously with a plurality of antennas. MIMO is an abbreviation for Multi Input Multi Output.

As shown in FIG. 1, the radar device 1 includes a transmitting unit 2, a transmitting antenna unit 3, a receiving antenna unit 4, a receiving unit 5, and a processing unit 6.
The transmitting antenna unit 3 has M transmitting antennas. M is an integer greater than or equal to 2. Each transmitting antenna is arranged in a row along a preset array direction with a preset _{first spacing d T.} In the present embodiment, the arrangement direction is the width direction of the vehicle.

The receiving antenna unit 4 has N receiving antennas. N is an integer greater than or equal to 2. Each receiving antenna has a _{second spacing d R} , which is different from _{the first spacing d T,} and is arranged along the same direction as the arrangement direction of the transmitting antennas.

Here, the signal received by each receiving antenna when M = 2 and N = 2 will be described. As shown in FIG. 2, it is assumed that the object to be detected exists in a direction inclined by an angle θ with respect to the front direction of the transmitting antenna unit 3 and the receiving antenna unit 4. Further, the reflection coefficient of the object is represented by D, the phase change of the signal in the path from the transmitting antenna TX1 to the object is _{represented by α T} , and the phase change of the signal in the path from the object to the receiving antenna RX1 is represented _{by α R.} It should _{be noted that α T} and α _R are represented by complex numbers.

In this case, the signal transmitted from the transmitting antenna TX1 and received by the receiving antenna RX1 is represented by the equation (1). The signal transmitted from the transmitting antenna TX1 and received by the receiving antenna RX2 is represented by the equation (2). The signal transmitted from the transmitting antenna TX2 and received by the receiving antenna RX1 is represented by the equation (3). The signal transmitted from the transmitting antenna TX2 and received by the receiving antenna RX2 is represented by the equation (4).

これらの式は、図３に示すように、４つの受信アンテナを、基準となる一つの受信アンテナからの距離が、それぞれｄ_Ｒ，ｄ_Ｔ，ｄ_Ｔ＋ｄ_Ｒとなる位置に並べた場合と等価である。図３では、最も左に位置する受信アンテナを基準としている。このように並んだ仮想的な受信アンテナ（以下、仮想受信アンテナ）を仮想アレーという。

As shown in FIG. 3, these equations are equivalent to arranging four receiving antennas at positions where the distances from one reference receiving antenna are d _R , d _T , and d _T + d _{R, respectively.} Is. In FIG. 3, the receiving antenna located on the far left is used as a reference. Virtual receiving antennas arranged in this way (hereinafter referred to as virtual receiving antennas) are referred to as virtual arrays.

In MIMO radar, by using a virtual array, the same angular resolution as when one transmitting antenna and M × N receiving antennas are provided is realized by M + N transmitting antennas and receiving antennas.

In this embodiment, as shown in FIG. 4, d _T = 3d and d _R = 2d. d is the minimum interval of the virtual array. In FIG. 4, M = 2 is set for simplification of the illustration. That is, FIG. 4 shows a virtual array when two transmitting antennas TX1 and TX2 and N receiving antennas RX1, RX2, ... RXN are arranged along the arrangement direction.

As a result, a virtual array is formed in which 2N virtual receiving antennas VRX_1, VRX_2, VRX_3, VRX_4, ..., VRX_2N-3, VRX_2N-2, VRX_2N-1, VRX_2N are arranged along the arrangement direction. The distance between the virtual receiving antenna VRX_1 and the virtual receiving antenna VRX_2 and the distance between the virtual receiving antenna VRX_2N-1 and the virtual receiving antenna VRX_2N are 2d. The distance between the other adjacent virtual receiving antennas is d.

As shown in FIG. 1, the transmission unit 2 includes an oscillation unit 21 and a modulation unit 22. The oscillator 21 generates a continuous wave common signal. The oscillation unit 21 supplies the generated common signal to the modulation unit 22 and also supplies the local signal L to the reception unit 5. Further, as shown in FIG. 5, the oscillation unit 21 has a chirp whose frequency changes continuously during the measurement period Tm (for example, 10 ms) at the beginning of each frame, with the measurement cycle Tf (for example, 50 ms) as one frame. The signal is repeatedly generated every repetition period Tp (for example, 50 μs).

The oscillation unit 21 is configured so that the measurement cycle Tf, the measurement period Tm, and the repeat cycle Tp can be appropriately changed according to the instruction from the processing unit 6. The frequency width of the chirp signal changed during the repetition period is constant regardless of the repetition period Tp. That is, by changing the repetition period Tp, the rate of change Δf of the frequency of the chirp signal is configured to change.

Further, the permissible range of the repeat period Tp, and thus the permissible range of the frequency change rate Δf of the chirp signal, depends on the relative speed with the object when the beat signal generated by mixing the transmission signal and the reception signal is analyzed. The frequency deviation that occurs is set to be negligible compared to the frequency deviation that occurs depending on the distance to the object.

The modulation unit 22 branches the common signal generated by the oscillation unit 21 to generate M branch signals, which is the same number as the transmission antennas belonging to the transmission antenna unit 3. The modulation unit 22 performs phase shift keying for each of the M branch signals to change the phase of the branch signals for each repeat period Tp. As a result, M transmission signals supplied to each of the transmission antennas are generated. In phase shift keying, a phase rotation amount Δφ having a magnitude different from that of each of the M branch signals is set, and the phase of the branch signal is rotated by the phase rotation amount Δφ for each repetition period.

Here, let P be the number of phases used in phase shift keying. P is an integer greater than M. In the modulation unit 22, P-type phase rotation amount represented by Δφ = p × 360 ° / P is used as p = 0, 1, 2, ... P-1. For example, when P = 4, as shown in FIG. 6, when p = 0, Δφ = 0 °, and the position of the transmission signal which is the signal after modulation with respect to the branch signal (that is, the common signal) which is the signal before modulation. The phase difference is 0 ° at all repetition periods Tp. When p = 1, Δφ = 90 °, and the phase difference of the transmitted signal with respect to the common signal is switched for each repetition period Tp, and changes in the order of 0 ° → 90 ° → 180 ° → 270 ° → 0 ° (the same applies hereinafter). When p = 2, Δφ = 180 °, and the phase difference of the transmitted signal with respect to the common signal is switched for each repeat cycle, and changes in the order of 0 ° → 180 ° → 0 ° → 180 ° → 0 ° (the same applies hereinafter). When p = 3, Δφ = 270 °, and the phase difference of the transmitted signal with respect to the common signal is switched for each repeat cycle, and changes in the order of 0 ° → 270 ° → 180 ° → 90 ° → 0 ° (the same applies hereinafter).

Since P> M is set as described above, not all types of P-type phase rotation amount Δφ are used for phase shift keying, but some of them are used.
The modulation unit 22 sets the number of phases P, selects M types of phase rotation amount to be used for phase shift modulation among P types of phase rotation amount Δφ, selects M types of phase rotation amount, and transmits M pieces. It is configured so that the setting of the correspondence relationship with the antenna can be changed as appropriate. The setting may be changed according to the instruction from the processing unit 6 or may be changed automatically. When changing automatically, it may be performed according to a predetermined pattern or may be performed randomly.

As shown in FIG. 1, the receiving unit 5 generates and generates a beat signal, which is a difference signal from the local signal L, for each of the N received signals output from each receiving antenna belonging to the receiving antenna unit 4. The beat signal is sampled and supplied to the processing unit 6. Hereinafter, configurations for generating each beat signal from the received signal corresponding to each receiving antenna (for example, a mixer, an amplifier, and an AD converter provided corresponding to each receiving antenna) are collectively provided as a receiving channel. Called.

The processing unit 6 is an electronic control device mainly composed of a well-known microcomputer provided with a CPU 61, a memory 62, and the like. The memory 62 is, for example, a ROM, a RAM, or the like. Various functions of the microcomputer are realized by the CPU 61 executing a program stored in a non-transitional substantive recording medium. In this example, the memory 62 corresponds to a non-transitional substantive recording medium in which the program is stored. In addition, by executing this program, the method corresponding to the program is executed. A part or all of the functions executed by the CPU 61 may be configured in hardware by one or a plurality of ICs or the like. Further, the number of microcomputers constituting the processing unit 6 may be one or a plurality.

Next, the procedure of the object detection process executed by the processing unit 6 will be described. The object detection process is a process that is repeatedly executed after the processing unit 6 is activated.
When this object detection process is executed, as shown in FIG. 7, the processing unit 6 first sets the repeat period Tp, which is a parameter related to the common signal generated by the oscillation unit 21, in S110. As described above, when the repetition period is changed, the rate of change Δf of the frequency of the chirp signal changes. The repeat cycle Tp may be a fixed value, and each time this process is executed, the repeat cycle Tp is set according to a predetermined pattern or randomly selected from a plurality of types of values. You may do so. Further, in S110, the measurement cycle Tf and the measurement period Tm may be appropriately variably set.

The processing unit 6 sets the number of phases P used for phase shift keying in the modulation unit 22 in S120. As the number of phases P, a value larger than at least the number of transmitting antennas M is used. For example, P = M + 1 may be set. Similar to the repeat period Tp, the number of phases P may be a fixed value, and each time this process is executed, the number of phases is selected according to a predetermined pattern or randomly selected from a plurality of types of values. P may be set.

In S130, the processing unit 6 selects M types of phase rotation amounts used for phase shift keying in the modulation unit 22 from among P types of phase rotation amounts determined by the number of phases P. The M types of phase rotation amounts are selected so that the respective rotation amounts are not evenly arranged in 360 °, that is, the arrangement is non-uniform.

Specifically, when P and M do not have a common divisor, the phase rotation amount can be arbitrarily selected. When P and M have common divisors, it is necessary to carefully select them so that the arrangement intervals do not repeat the same pattern.

For example, as shown in FIG. 8, when P = 4 and M = 2, the combination of phase rotation amounts is (0 °, 90 °), (90 °, 180 °), (180 °, 270 °). , (270 °, 0 °) can be selected, but (0 °, 180 °) and (90 °, 270 °) cannot be selected. When P = 4 and M = 3, the combinations of phase rotation amounts are (0 °, 90 °, 180 °), (90 °, 180 °, 270 °), (180 °, 270 °, 0). °), (270 °, 0 °, 90 °) can all be selected. However, in this embodiment, a combination including Δφ = 0 ° is always selected.

The selection of the phase rotation amount may be constant at all times, or may be switched according to a predetermined pattern or randomly among the selectable combinations each time the present process is executed.

In S140, the processing unit 6 sets the correspondence between the M types of phase rotation amounts selected in S130 and each transmitting antenna. This association may be assigned according to a preset rule, for example, or may be randomly assigned. Further, the association may always be constant, or may be switched according to a predetermined pattern or randomly each time the present process is executed.

In FIG. 9, P = 4 and M = 2, (0 °, 90 °) is selected as the combination of the phase rotation amounts, and Δφ = 0 ° is assigned to the transmitting antenna TX1 and Δφ = 90 ° is assigned to the transmitting antenna TX2. In this case, the phase of the transmission signal supplied to each of the transmission antennas TX1 and TX2 changes.

The processing unit 6 determines in S150 whether or not it is the measurement start timing. If it is not the measurement start timing, the processing unit 6 waits by repeating the process of S150 until the measurement start timing is reached. When it is the measurement start timing, the processing unit 6 shifts to S160. The measurement start timing is the timing at which the frame whose length is determined by the measurement cycle Tf is switched.

After shifting to S160, the processing unit 6 operates the transmitting unit 2 according to the setting results in S110 to S140 to perform radar measurement. Specifically, the transmission unit 2 is made to repeatedly transmit the chirp signal for each repeat cycle Tp during the measurement period Tm, and obtains the sampling result of the beat signal generated from the received signal. Hereinafter, the number of chirp signals repeatedly transmitted during the measurement period Tm is defined as K.

In S170, the processing unit 6 performs frequency analysis of the sampling results of the beat signals obtained from the N receiving antennas for each receiving antenna and each chirp signal, so that each of the N receiving antennas is K. Calculate the distance spectrum for each piece. In each distance spectrum, a peak appears at a frequency corresponding to the time required to reciprocate the object reflecting the radiated wave transmitted from the transmitting antenna (that is, the distance to the object).

The processing unit 6 calculates the velocity spectrum for each receiving antenna in S180 using the N × K distance spectra calculated in S170. Specifically, signals of the same frequency bin are extracted from K distance spectra of the receiving antenna of interest, and frequency analysis processing is executed on the extracted signals in the time axis direction. This process is performed for all frequency bins (ie, distances).

In the velocity spectrum, when the relative velocity with respect to the object reflecting the radiated wave from the transmitting antenna unit 3 is zero, the frequency corresponding to the phase rotation amount assigned to each transmitting antenna is extracted as the Doppler frequency. That is, the frequency of the signal component corresponding to Δφ = 0 ° is 0 Hz.

The range in which the Doppler frequency is observed (hereinafter referred to as the Doppler observation range) is determined by the repetition period Tp. Further, as shown in FIG. 10, the Doppler frequency is detected at M points among the points where the Doppler observation range is divided into P. In FIG. 10, the upper limit of the Doppler observation range is normalized to 1.

Further, in the velocity spectrum, when there is a relative velocity with the object, these M Doppler frequencies are shifted by a magnitude corresponding to the relative velocity, and frequency wrapping occurs depending on the magnitude of the relative velocity. do.

From the calculation results of S170 and S180, a two-dimensional spectrum (hereinafter, reception spectrum) representing the distance and relative velocity to the object reflecting the radar wave is generated for each receiving antenna.

As shown in FIG. 7, in S190, the processing unit 6 calculates the distance and relative velocity to the object reflecting the radar wave and the direction in which the object exists by using the reception spectrum for each receiving antenna. The information generation process is executed and the object detection process is terminated.

Next, the procedure of the information generation process executed in S190 will be described.
When the information generation process is executed, as shown in FIG. 11, the processing unit 6 first incoherently integrates the N reception spectra generated for each receiving antenna in S310 in S310, and then performs one. Two integrated spectra g (r, v) are calculated. Assuming that the reception spectrum for each receiving antenna is represented by s (r, v, Rch), the integrated spectrum g (r, v) is calculated using the equation (5). r is a distance, v is a normalized Doppler velocity with the velocity corresponding to the upper limit frequency of the Doppler observation range as 1, and Rch is a number for identifying the receiving antenna.

処理部６は、Ｓ３２０にて、統合スペクトラム上で、予め設定された閾値以上の強度を有するピークがＭ個以上検出されている距離を候補距離として、候補距離のうち、以下のＳ３３０からＳ３８０での処理の対象として未だ選択されていない距離を、対象距離ｒとして選択する。

The processing unit 6 sets the distance at which M or more peaks having an intensity equal to or higher than a preset threshold value are detected in S320 on the integrated spectrum as candidate distances, and among the candidate distances, from S330 to S380 below. A distance that has not yet been selected as the target of the processing of is selected as the target distance r.

The processing unit 6 sets the target speed corresponding to the peaks not yet selected as the processing targets in S340 to S370 below among the plurality of peaks detected at the target distance r selected in S320 in S330. Select as v. Here, the speed is selected in ascending order.

In S340, the processing unit 6 assumes that the peak of the target velocity v is the peak corresponding to the phase rotation amount Δφ = 0 °, and there is a peak corresponding to another phase rotation amount according to the equation (6). Then, the corresponding points (r, vj) of M-1 which are estimated, where j = 2 to M are calculated. x (j) is a phase rotation amount other than Δφ = 0 ° selected in S130. v and vj are normalized Doppler frequencies and take a value between 0 and 1. mod (a, m) indicates the remainder after dividing a by m.

処理部６は、Ｓ３５０にて、Ｓ３４０で推定された対応点の全てについて、統合スペクトラム上でピーク（すなわち、二次極大点）が存在するか否かを判断し、肯定判断された場合はＳ３６０に移行し、否定判断された場合は、Ｓ３９０に移行する。以下では、対応点に対応するＭ個のピークを候補ピーク群という。

The processing unit 6 determines in S350 whether or not there is a peak (that is, a secondary maximum point) on the integrated spectrum for all the corresponding points estimated in S340, and if affirmatively determined, S360. If a negative judgment is made, the process proceeds to S390. In the following, M peaks corresponding to the corresponding points are referred to as candidate peak groups.

When shifting to S360, the processing unit 6 determines whether or not the candidate peak group satisfies the power condition, and if a positive judgment is made, the process proceeds to S370, and if a negative judgment is made, the process proceeds to S390. Here, as the power condition, it is used that the signal intensity difference of the peaks belonging to the candidate peak group is within a preset allowable range. This is based on the finding that the signal intensities of peaks based on reflected waves from the same object should all be similar.

Upon transition to S370, the processing unit 6 determines whether or not the candidate peak group satisfies the phase condition, and if a positive determination is made, the process proceeds to S380, and if a negative determination is made, the process proceeds to S390. Here, as the phase condition, the phase difference between the reference reception channel and the other reception channels is calculated, and it is used that the difference in the phase difference between the candidate peaks is within a preset allowable range. This is based on the knowledge that peaks based on reflected waves from the same object should all come from the same direction, and the phase differences between receptions of peaks coming from the same direction are all similar in magnitude. Based on the fact that it becomes. In the following, the candidate peak group that is positively judged in 370 is referred to as the same object peak group.

After shifting to S380, the processing unit 6 registers the set of the target distance r and the target velocity v as object information. Further, the processing unit 6 also adds the direction θ calculated as follows to the object information. That is, each peak corresponding to the same object peak group of M is extracted from each of the N reception spectrums calculated for each receiving antenna. The extracted M × N peaks are regarded as the received signals from the M × N receiving antennas included in the virtual array, and the direction θ of the object is θ by executing the direction detection process such as MUSIC or beamforming. Is calculated. MUSIC is an abbreviation for Multiple signal classification.

It should be noted that each M peak extracted as the same object peak group from each of the received signals of the N receiving antennas corresponds to M × N received signals obtained from the virtual array.
When shifting to S390, the processing unit 6 determines whether or not all the peaks (that is, velocities) detected at the target distance r are selected as the target speed v, and if affirmatively determined, shifts to S400. If a negative judgment is made, the process proceeds to S330.

Upon shifting to S400, the processing unit 6 determines whether or not all the candidate distances have been selected as the target distance r. If a positive judgment is made, the information generation process is terminated, and if a negative judgment is made, S320 Move to.

The radar device 1 configured in this way includes a transmitting antenna unit 3, an oscillating unit 21, a modulation unit 22, a receiving antenna unit 4, and a processing unit 6.
Transmitting antenna unit 3 includes the first interval d _T set in advance, the M transmit antennas are arranged in a row along a predetermined arrangement direction. The oscillator 21 generates a continuous wave common signal. The modulation unit 22 has a phase rotation amount different for each of the M branched signals obtained by branching the common signal to the same number as the M transmitting antennas, and the phase of the branched signal for each preset repetition period Tp. By performing phase shift keying to rotate the above, M transmission signals input to a plurality of transmission antennas are generated. The receiving antenna unit 4 has N receiving antennas arranged in a line along the arrangement direction with a second spacing d _{R set differently from the first spacing d T.} The processing unit 6 emits waves from the transmitting antenna unit 3 based on a plurality of signal components corresponding to the M transmitted signals extracted from each of the N received signals received by the receiving antenna unit 4. Generates object information about the object that reflected.

Then, in the radar device 1, the virtual array in which a plurality of virtual receiving antennas are arranged in a row along the arrangement direction is formed by the M transmitting antennas and the N receiving antennas. Further, the first interval d _T is equal to the multiplication value of the minimum interval d, which is the minimum value of the arrangement intervals of the plurality of virtual receiving antennas, and the first multiple, which is an integer of 2 or more, and the second interval is the minimum interval. It is equal to the multiplication value of d and a second multiple that is an integer greater than or equal to 2 and is set to be different from the first multiple. In the present embodiment, the first multiple is 3, the second multiple is 2, and the first and second multiples are relatively prime.

As described above, in the radar device 1, the arrangement interval of N receiving antennas is more than twice the arrangement interval of the virtual receiving antennas, and the physical receiving channel interval can be widened. Therefore, the isolation between the receiving channels is performed. Can be improved, and the accuracy of detecting the orientation of the object can be improved.

Further, the radar device 1 of the present embodiment can improve the accuracy of target orientation estimation in a situation where the target signal and the mirror ghost signal are superimposed.
When the direction is estimated using MIMO, the direction scan is performed with the transmission steering vector indicating the direction of the transmission signal and the reception steering vector indicating the direction of the reception signal aligned in the same direction.

In the signal reflected by the true target and directly received by the receiving antenna (hereinafter referred to as the target signal), the transmission steering vector and the reception steering vector face the direction in which the true target exists. On the other hand, in a mirror ghost signal (for example, a signal received in the path of transmitting antenna → target → wall → receiving antenna), the transmitting steering vector points in the direction in which the true target exists, and the receiving steering vector has a wall. It is facing the direction.

Therefore, the directional spectrum of the mirror ghost signal obtained for each of the plurality of virtual receiving antennas has a periodic error for each angle corresponding to the distance between the transmitting antennas. This periodic error occurs due to the mismatch between the orientation of the transmit steering vector and the orientation of the receive steering vector. In the above directional spectrum, the horizontal axis is the azimuth and the vertical axis is the signal strength, and the distribution of the signal strength for each direction is shown.

FIG. 12 is a diagram showing an estimated locus of a target in the arrangement of the MIMO antennas of the conventional and the present embodiment. Graph G1 shows the estimated locus of the target in the conventional MIMO antenna arrangement. Graph G2 shows the estimated locus of the target in the arrangement of the MIMO antenna of the present embodiment.

In the graphs G1 and G2, the own vehicle MC equipped with the radar device 1 is arranged at the position of (x, y) = (0 [m], 0 [m]), and (x, y) = (2 [m]). ], 0 to 200 [m]), the estimated locus of the target approaching the own vehicle MC is indicated by a plurality of circles as shown in the movement locus L1.

In the graph G1, M = 2, N = 6, d _T = 6d, d _R = d as the arrangement of the conventional MIMO antennas. In the graph G2, the arrangement of the MIMO antennas of the present embodiment is M = 2, N = 6, d _T = 3d, d _R = d2.

In the conventional MIMO antenna arrangement, since the distance between the transmitting antennas adjacent to each other is wide, the periodic error of the mirror ghost signal becomes low frequency and is concentrated around the direction of the mirror ghost signal. By concentrating the periodic error of the mirror ghost signal around the direction of the mirror ghost signal, the intensity of the error increases around the direction of the mirror ghost signal. The directional difference between the target signal and the mirror ghost signal is small. Therefore, it becomes difficult to separate the target signal and the mirror ghost signal.

On the other hand, in the arrangement of the MIMO antennas of the present embodiment, since the distance between the transmitting antennas adjacent to each other is narrow, the periodic error of the mirror ghost signal becomes high frequency and is dispersed in a wide directional range. Therefore, even if the directional difference between the target signal and the mirror ghost signal is small, the influence of the error generated around the directional of the mirror ghost signal is small, and the target signal and the mirror ghost signal can be easily separated.

As shown in graph G1, in the conventional MIMO antenna arrangement, the movement locus of the target and the estimated locus substantially match at the position of (x, y) = (0 [m], 0 to 20 [m]). ing. On the other hand, as shown in the graph G2, in the arrangement of the MIMO antenna of the present embodiment, the movement locus and the estimated locus of the target are obtained at the position of (x, y) = (0 [m], 0 to 70 [m]). Are almost the same. As described above, the radar device 1 of the present embodiment can estimate the direction of the target more accurately as compared with the arrangement of the conventional MIMO antenna.

Further, the radar device 1 of the present embodiment can improve the accuracy of target orientation estimation in a situation where a plurality of targets exist. As shown in FIG. 13, for example, the radar device 1 of the present embodiment has a target orientation in a state where an interference wave is superimposed on only the received signal by one of the transmitting antennas among the received signals by the transmitting antennas TX1 and TX2. The estimation accuracy can be improved.

FIG. 14 shows the directional spectrum when the target azimuth is estimated by using the MUSIC method in the arrangement of the MIMO antennas of the conventional and the present embodiment. Graph G3 shows the directional spectrum in a conventional MIMO antenna arrangement. Graph G4 shows the directional spectrum in the arrangement of the MIMO antennas of this embodiment.

In the conventional MIMO antenna arrangement, since the distance between the transmitting antennas adjacent to each other is wide, the signal components of the interference wave signal are concentrated around the interference wave direction, and the interference wave peak is set to that direction as shown in Graph G3. It will be detected.

On the other hand, in the arrangement of the MIMO antennas of the present embodiment, since the distance between the transmitting antennas adjacent to each other is narrow, the signal components of the interference wave azimuth spectrum are dispersed in a wide direction, and as shown in the graph G4, the interference wave peak is generated. It becomes difficult to detect.

Further, in the radar device 1, _{the difference between the first interval d T} and the second interval d _R is equal to the minimum interval d. This facilitates the work of the radar device 1 designer to determine _{the first interval d T} and the second interval d _R such that the first and second multiples are relatively prime. be able to.

Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and can be implemented in various modifications.
[Modification 1]
For example, in the above embodiment, the embodiment in which d _T = 3d and d _R = 2d is shown. However, the first interval d _T is equal to the multiplication value of the minimum interval d of the virtual array and the first multiple which is an integer of 2 or more, and the second interval d _R is the minimum interval d and an integer of 2 or more. It is sufficient that the first multiple and the second multiple are relatively prime to each other and are equal to the multiplication value with the second multiple set so as to be different from the first multiple. For example, as shown in FIG. 15, d _T = 2d and d _R = 3d may be used, or as shown in FIG. 16, d _T = 3d and d _R = 4d, which are shown in FIG. As described above, d _T = 3d and d _R = 5d may be satisfied. As shown in FIGS. 15 to 17, in any of the above cases, the minimum interval of the virtual array is d.

[Modification 2]
In the above embodiment, the transmitting antenna and the receiving antenna are arranged in a row along the width direction of the vehicle. However, as shown in FIG. 18, the transmitting antenna and the receiving antenna may be arranged in a row along the height direction DH of the vehicle. As a result, the radar device 1 performs the target signal in a situation where the target signal and the mirror ghost signal caused by the reflection on the road (that is, the signal received in the path of the transmitting antenna → the target → the road → the receiving antenna) are superimposed. It is possible to improve the orientation estimation accuracy of.

[Modification 3]
In the above embodiment, the transmitting antenna and the receiving antenna are arranged in a row along the width direction of the vehicle. However, as shown in FIG. 19, the transmitting antenna and the receiving antenna may be formed in a matrix. That is, in the transmitting antenna unit 3, a plurality of transmitting antennas are _{arranged at the first interval d T along the arrangement direction and at the first interval d T} along the vertical arrangement direction perpendicular to the arrangement direction. Will be done. The receiving antenna unit 4, a plurality of receiving antennas, while being arranged at a second distance d _R in the arrangement direction, are arranged at a second distance d _R along the vertical arrangement direction. As a result, the radar device 1 can detect the position of the object in three dimensions instead of two dimensions. For example, when the arrangement direction is the width direction of the vehicle and the vertical arrangement direction is the height direction of the vehicle, the object is determined by the position along the width direction of the vehicle and the position along the height direction of the vehicle. The position of can be detected in three dimensions.

Further, the function of one component in the above embodiment may be shared by a plurality of components, or the function of the plurality of components may be exerted by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

In addition to the radar device 1 described above, the present disclosure can be realized in various forms such as a system having the radar device 1 as a component.

1 ... Radar device, 2 ... Transmission unit, 3 ... Transmission antenna unit, 4 ... Reception antenna unit, 5 ... Reception unit, 6 ... Processing unit, 21 ... Oscillation unit, 22 ... Modulation unit

Claims (4)

A transmitting antenna unit (3) having a plurality of transmitting antennas arranged in a row along a preset arrangement direction at a preset first interval, and a transmitting antenna unit (3).
Oscillator (21) that generates a common signal of continuous waves,
For each of the plurality of branched signals obtained by branching the common signal to the same number as the plurality of transmitting antennas, the phase shift that rotates the phase of the branched signal at each preset repetition period with a different phase rotation amount. By performing phase shift keying, a modulation unit (22) that generates a plurality of transmission signals input to the plurality of transmission antennas, and a modulation unit (22).
A receiving antenna unit (4) having a plurality of receiving antennas arranged in a row along the arrangement direction at a second interval set differently from the first interval, and a receiving antenna unit (4).
Information about an object that reflects a radiated wave from the transmitting antenna unit based on a plurality of signal components corresponding to the plurality of transmitting signals extracted from each of the plurality of received signals received by the receiving antenna unit. Equipped with a processing unit (6) to generate
The plurality of transmitting antennas and the plurality of receiving antennas form a virtual array in which a plurality of virtual receiving antennas are arranged in a row along the arrangement direction.
The first interval is equal to the multiplication value of the minimum interval, which is the minimum value of the arrangement interval of the plurality of virtual receiving antennas, and the first multiple, which is an integer of 2 or more.
The second interval is equal to the multiplication value of the minimum interval and a second multiple that is an integer of 2 or more and is set to be different from the first multiple.
A radar device (1) in which the first multiple and the second multiple are coprime. The radar device according to claim 1.
A radar device in which the difference between the first interval and the second interval is equal to the minimum interval. The radar device according to claim 1 or 2.
The radar device is mounted on the vehicle and
The arrangement direction is a radar device that is the height direction of the vehicle. The radar device according to any one of claims 1 to 3.
In the transmitting antenna unit, the plurality of transmitting antennas are arranged at the first interval along the arrangement direction and at the first interval along the vertical arrangement direction perpendicular to the arrangement direction. By doing so, it is formed in a matrix.
The receiving antenna unit is arranged in a matrix by arranging the plurality of receiving antennas at the second interval along the arrangement direction and at the second interval along the vertical arrangement direction. Radar device formed.

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